org.apache.jasper.xmlparser

Class SymbolTable

public class SymbolTable extends Object

This class is a symbol table implementation that guarantees that strings used as identifiers are unique references. Multiple calls to addSymbol will always return the same string reference.

The symbol table performs the same task as String.intern() with the following differences:

A new string object does not need to be created in order to retrieve a unique reference. Symbols can be added by using a series of characters in a character array.
Users of the symbol table can provide their own symbol hashing implementation. For example, a simple string hashing algorithm may fail to produce a balanced set of hashcodes for symbols that are mostly unique. Strings with similar leading characters are especially prone to this poor hashing behavior.

Version: $Id: SymbolTable.java 466606 2006-10-21 23:07:12Z markt $

Author: Andy Clark

Nested Class Summary
protected static class	SymbolTable.Entry This class is a symbol table entry.

Field Summary
protected SymbolTable.Entry[]	fBuckets Buckets.
protected int	fTableSize
protected static int	TABLE_SIZE Default table size.

Constructor Summary
	SymbolTable() Constructs a symbol table with a default number of buckets.
	SymbolTable(int tableSize) Constructs a symbol table with a specified number of buckets.

Method Summary
String	addSymbol(String symbol) Adds the specified symbol to the symbol table and returns a reference to the unique symbol.
String	addSymbol(char[] buffer, int offset, int length) Adds the specified symbol to the symbol table and returns a reference to the unique symbol.
boolean	containsSymbol(String symbol) Returns true if the symbol table already contains the specified symbol.
boolean	containsSymbol(char[] buffer, int offset, int length) Returns true if the symbol table already contains the specified symbol.
int	hash(String symbol) Returns a hashcode value for the specified symbol.
int	hash(char[] buffer, int offset, int length) Returns a hashcode value for the specified symbol information.

Field Detail

fBuckets

protected SymbolTable.Entry[] fBuckets

Buckets.

TABLE_SIZE

protected static final int TABLE_SIZE

Default table size.

Constructor Detail

SymbolTable

public SymbolTable()

Constructs a symbol table with a default number of buckets.

SymbolTable

public SymbolTable(int tableSize)

Constructs a symbol table with a specified number of buckets.

Adds the specified symbol to the symbol table and returns a reference to the unique symbol. If the symbol already exists, the previous symbol reference is returned instead, in order guarantee that symbol references remain unique.

Parameters: symbol The new symbol.

addSymbol

public String addSymbol(char[] buffer, int offset, int length)

Parameters: buffer The buffer containing the new symbol. offset The offset into the buffer of the new symbol. length The length of the new symbol in the buffer.

containsSymbol

public boolean containsSymbol(String symbol)

Returns true if the symbol table already contains the specified symbol.

Parameters: symbol The symbol to look for.

containsSymbol

public boolean containsSymbol(char[] buffer, int offset, int length)

Returns true if the symbol table already contains the specified symbol.

Parameters: buffer The buffer containing the symbol to look for. offset The offset into the buffer. length The length of the symbol in the buffer.

hash

public int hash(String symbol)

Returns a hashcode value for the specified symbol. The value returned by this method must be identical to the value returned by the hash(char[],int,int) method when called with the character array that comprises the symbol string.

Parameters: symbol The symbol to hash.

hash

public int hash(char[] buffer, int offset, int length)

Returns a hashcode value for the specified symbol information. The value returned by this method must be identical to the value returned by the hash(String) method when called with the string object created from the symbol information.

Parameters: buffer The character buffer containing the symbol. offset The offset into the character buffer of the start of the symbol. length The length of the symbol.